Nicole Richie has sparked reports her wedding to rocker Joel Madden is imminent after whisking her closest female friends off for a Mexican bachelorette party.Christina Aguilera and DJ Sam Ronson were among the pals who joined the socialite, jeweller and reality TV star for the weekend (18-19Sep10) Cabo San Lucas getaway. According to People.com, the girls relaxed by the Las Ventanas resort pool and enjoyed a series of spa treatments. There was also a celebration dinner. Absent was Richie's former best friend and The Simple Life co-star Paris Hilton. Richie and Madden, who are the parents of two young children, have yet to reveal when they'll wed.